Creating a script for a Telnet session?

Question

Does anyone know of an easy way to create a script that can connect to a telnet server, do some usual telnet stuff, and then log off? I am dealing with users who are not fa

Answer 1

Expect is built for this and can handle the input/output plus timeouts etc. Note that if you're not a TCL fan, there are Expect modules for Perl/Python/Java.

EDIT: The above page suggests that the Wikipedia Expect entry is a useful resource :-)

Answer 2

I've used various methods for scripting telnet sessions under unix, but the simplest one is probably a sequence of echo and sleep commands, with their output piped into telnet. Piping the output into another command is also a possibility.

Silly example

(echo password; echo "show ip route"; sleep 1; echo "quit" ) | telnet myrouter

This (basicallly) retrieves the routing table of a Cisco router.

Answer 3

Couple of questions:

1. Can you put stuff on the device that you're telnetting into?
2. Are the commands executed by the script the same or do they vary by machine/user?
3. Do you want the person clicking the icon to have to provide a userid and/or password?

That said, I wrote some Java a while ago to talk to a couple of IP-enabled power strips (BayTech RPC3s) which might be of use to you. If you're interested I'll see if I can dig it up and post it someplace.

Answer 4

I like the example given by Active State using python. Here is the full link. I added the simple log in part from the link but you can get the gist of what you could do.

import telnetlib

prdLogBox='142.178.1.3'
uid = 'uid'
pwd = 'yourpassword'

tn = telnetlib.Telnet(prdLogBox)
tn.read_until("login: ")
tn.write(uid + "\n")
tn.read_until("Password:")
tn.write(pwd + "\n")
tn.write("exit\n")
tn.close()

Answer 5

Another method is to use netcat (or nc, dependent upon which posix) in the same format as vatine shows or you can create a text file that contains each command on it's own line.

I have found that some posix' telnets do not handle redirect correctly (which is why I suggest netcat)